Hi DavidR & wyrmrider,
Thanks for the replies . . .
DavidR - the file name for the dummy virus is eicar.com; it was created according to the instructions here
http://www.avast.com/eng/eicar-antivirus-test-file.html. The scan was a standard local disks scan with archives.
And no, I cannot tell the on-demand scan where to start, but the avast! user interface does report where it is working at any given moment. That's how I noticed that it always starts with the windows drivers folder.
And to wyrmrider, yeah, I know, a minute. But hey, at my age, every minute is precious . . .
Anyway, I'm still concerned that avast! doesn't report the virus when scanning the drivers folder at the beginning of a 'Local disks' scan.
Today it occurred to me to try doing just a folder scan of the drivers folder. Lo and behold, the virus is discovered. So now I'm doubly confused.
Is it possible that the reported scan of the windows drivers folder isn't really scanning the full folder but rather some subset (even though it seems to count up to around the total number of files in the folder before switching to the next location)? If so, does that leave a vector open for the bad guys?
If anybody knows . . .
Thanks again,
tommyj